The effect of vortex angle on the efficiency of the Ranque–Hilsch vortex tube

A Ranque–Hilsch vortex tube is a long hollow cylinder with tangential nozzle placed near one end for injection of compressed air. The flow inside the vortex tube can be described as rotating air, which moves as a helical vortex flow. The peripheral flow moves toward the hot end, where the central part of the tube is blocked by a plug. The axial flow, which is forced back by the central part of the hot end plug, moves in the opposite direction toward the cold end. This paper focuses on the effect of the angle of rotating flow on the performance and efficiency of the Ranque–Hilsch vortex tube. To find the effect of vortex angle, different vortex angle generators were used and the best configuration was found.     

The effect of dynamic normal force on the stick–slip vibration characteristics

Nonlinear Dynamics - In the experiment, we observed such a phenomenon: the alternating normal force changes the vibration state of a friction system. A single-degree-of-freedom mathematical model...     

The “Inverse Hall-Petch” effect on the impact response of single crystal copper

Based on the available experimental and computational capabilities, a phenomenological approach has been proposed to formulate a hypersurface in both spatial and temporal domains to predict combined specimen size and loading rate effects on the material properties [1-2]. A systematic investigation is being performed to understand the combined size, rate and thermal effects on the properties and deformation patterns of representative materials with different nanostructures and under various types of loading conditions [3- 16]. The recent study on the single crystal copper response to impact loading has revealed the size-dependence of the Hugoniot curve. In this paper, the "inverse Hall-Petch" behavior as observed in the impact response of single crystal copper, which has not been reported in the open literature, is investigated by performing molecular dynamics simulations of the response of copper nanobeam targets subjected to impacts by copper nanobeam flyers with different impact velocities. It appears from the preliminary results that the "inverse Hall-Petch" behavior in single crystal copper is mainly due to the formation and evolution of disordered atoms and the interaction between ordered and disordered atoms, as compared with the physics behind the "inverse Hall-Petch"behavior as observed in nanocrystalline materials.     

The effect of moisture-induced swelling on the absorption capacity of transversely isotropic elastic polymer–matrix composites

The interaction between humid air and transversely isotropic fiber-reinforced composites with swelling polymeric matrix is considered. A model is proposed for the water saturation level in a polymer when stresses are applied, that uses directly obtainable material parameters only. In a composite, the reinforcements modify the water uptake of the polymer matrix because of the internal stresses that are induced by its restricted swelling, and this effect is evaluated. As a consequence of the coupling between stresses and absorption capacity, the sorption isotherm of a composite is ruled by the (non-linear) Langmuir equation when the unreinforced matrix obeys the (linear) Henry’s law.     

The effect of concrete slab–rockfill interface behavior on the earthquake performance of a CFR dam

Earthquake response of the concrete slab is mostly depended upon its conjunction with rockfill. This study aims to reveal the effect of concrete slab–rockfill interface behavior on the earthquake performance of a concrete-faced rockfill dam considering friction contact and welded contact. Friction contact is provided by using interface elements with five numbers of shear stiffness values. 2D finite element model of Torul concrete-faced rockfill dam is used for this purpose. Linear and materially non-linear time-history analyses considering dam–reservoir interaction are performed using ANSYS. Reservoir water is modeled using fluid finite elements by the Lagrangian approach. The Drucker–Prager model is preferred for concrete slab and rockfill in non-linear analyses. Horizontal component of 1992 Erzincan earthquake with peak ground acceleration of 0.515g is used in analyses. The maximum and minimum displacements and principal stresses are shown by the height of the concrete slab and earthquake performance of the dam is investigated considering different joint conditions for empty and full reservoir cases. In addition, potential damage situations of concrete slab are evaluated.     

The effect of wall cooling on compressible Görtler vortices

It is known that in adiabatic boundary layer flow over a curved surface the detailed structure of the spanwise periodic Görtler vortex instability varies markedly over the range of spanwise wavelength. At short wavelengths the modes tend to be concentrated in a well-defined thin zone located within the boundary layer. As the vortex wavenumber diminishes so the region of vortex activity is first driven to the bounding wall but subsequently expands to cover the entire boundary layer at which stage the modes take on a principally inviscid form. At yet longer wavelengths the vortices are given by the solution of an interactive multi-deck structure which has some similarities with that for Tollmien–Schlichting waves.In this work we investigate how the application of wall cooling affects the above scenario. It is shown how cooling both restricts the range of mode types and gives rise to two new structures. The first, for moderate cooling and which relates to longer wavelengths, is interactive in nature. Here the viscous–inviscid interaction between an essentially inviscid Görtler problem, albeit for an effective basic flow which in its general form has a non-standard near-wall structure, and a viscous sublayer is provided by novel boundary conditions. Shorter wavelength vortices are largely unaffected by wall cooling unless this is quite severe. However when this degree of cooling is applied, the vortices take on a fully viscous form and are confined to a thin region next to the bounding wall wherein the basic flow assumes an analytic form. Numerical solutions are obtained and we provide evidence as to how the two new structures are related both to each other and to the previously known uncooled results.     

The effect of blade vibration on the nonlinear characteristics of rotor–bearing system supported by nonlinear suspension

In this paper, the complicated nonlinear dynamics of the harmonically forced quasi-zero-stiffness SD (smooth and discontinuous) oscillator is investigated via direct numerical simulations. This oscillator considered that the gravity is composed of a lumped mass connected with a vertical spring of positive stiffness and a pair of horizontally compressed springs providing negative stiffness, which can achieve the quasi-zero stiffness widely used in vibration isolation. The local and global bifurcation analyses are implemented to reveal the complex dynamic phenomena of this system. The double-parameter bifurcation diagrams are constructed to demonstrate the overall topological structures for the distribution of various responses in parameter spaces. Using the Floquet theory and parameter continuation method, the local bifurcation patterns of periodic solutions are obtained. Moreover, the global bifurcation mechanisms for the crises of chaos and metamorphoses of basin boundaries are examined by analysing the attractors and attraction basins, exploring the evolutions of invariant manifolds and constructing the basin cells. Meanwhile, additional nonlinear dynamic phenomena and characteristics closely related to the bifurcations are discussed including the resonant tongues, jump phenomena, amplitude–frequency responses, chaotic seas, transient chaos, chaotic saddles, and also their generation mechanisms are presented.     

The effect of short chain branching on the rheological and thermal properties of olefin: α-olefin copolymers

An important method of the modification of the properties of polyethylene and polypropylene is the copolymerisation with -olefins. The -olefin behaves as a short branch in the structure, and the rheological and thermal properties of copolymers change significantly. A new method is suggested to evaluate the rheological and thermal properties of copolymers on the basis of homopolymer properties, by introducing a short branch degree parameter. The zero shear viscosity, plateau modulus, fractional free volume, reptation tube diameter, glass transition temperature and thermodynamical melting point were calculated.     

The effect of crack size and specimen size on the relation between the Paris and Wöhler curves

Paris and Wöhler’s fatigue curves are intimately connected by the physics of the process of fatigue crack growth. However, their connections are not obvious due to the appearance of anomalous specimen-size and crack-size effects. In this study, considering the equations for a notched specimen (or for a specimen where failure is the result of the propagation of a main crack) and the assumption of incomplete self-similarity on the specimen size, the relations between the size-scale effects observed in the Paris and Wöhler’s diagrams are explained. In the second part of the work, the behaviour of physically short cracks is addressed and, considering a fractal model for fatigue crack growth, the crack-size effects on the Paris and Wöhler’s curves are discussed.     

The effect of pulsed harvesting policy on the inshore–offshore fishery model with the impulsive diffusion

In this paper, we propose the inshore–offshore fishing model with impulsive diffusion and pulsed harvesting at the different fixed time. The existence and globally asymptotical stability of both the trivial periodic solution and the positive periodic solution are obtained. We show that the pulsed harvesting has a strong impact on the persistence of the fish population. By the numerical simulation, we obtain that the best time of fishing is at the end of the period τ.     

The effect of microstructural morphology on the elastic,inelastic, and degradation behaviors of aluminum–alumina composites

Micromechanical models with idealized and simplified shapes of inhomogeneities have been widely used to obtain the average (macroscopic) mechanical response of different composite materials. The main purpose of this study is to examine whether the composites with irregular shapes of inhomogeneities, such as in the aluminum–alumina (Al–Al₂O₃) composites, can be approximated by considering idealized and simplified shapes of inhomogeneities in determining their overall macroscopic mechanical responses. We study the effects of microstructural characteristics, on mechanical behavior (elastic, inelastic, and degradation) of the constituents, and shapes and distributions of the pores and inclusions (inhomogeneities), and thermal stresses on the overall mechanical properties and response of the Al–Al₂O₃ composites. Microstructures of a composite with 20% alumina volume content are constructed from the microstructural images of the composite obtained by scanning electron microscopy (SEM). The SEM images of the composite are converted to finite element (FE) meshes, which are used to determine the overall mechanical response of the Al–Al₂O₃ composite. We also construct micromechanics model by considering circular shapes of the inhomogeneities, while maintaining the same volume contents and locations of the inhomogeneities as the ones in the micromechanics model with actual shapes of inhomogeneities. The macroscopic elastic and inelastic responses and stress fields in the constituents from the micromechanics models with actual and circular shapes of inhomogeneities are compared and discussed.     

The effect of G?rtler instability on hypersonic boundary layer transition

The evolution of G?rtler vortices and its interaction with other instabilities are investigated in this paper.Both the Mack mode and the G?rtler mode exist in hypersonic boundary-layer flows over concave surfaces, and their interactions are crucially important in boundary layer transition. We carry out a direct numerical simulation to explore the interaction between the G?rtler and the oblique Mack mode.The results indicate that the interaction between the forced G?rtler mode and the oblique Mack mode promotes the onset of the transition. The forced oblique Mack mode is susceptible to nonlinear interaction.Because of the development of the G?rtler mode, the forced Mack mode and other harmonic modes are excited.     

The effect of a dipolar structure on the Hölder stability in Green–Naghdi thermoelasticity

This study is concerned with the mixed initial boundary value problem for a dipolar body in the context of the thermoelastic theory proposed by Green and Naghdi. For the solutions of this problem we prove a result of Hölder’s-type stability on the supply terms. We impose middle restrictions on the thermoelastic coefficients, which are common in continuum mechanics. For the same conditions we propose a continuous dependence result with regard to the initial data.     

On the effect of the nozzle design on the performances of gas–liquid cylindrical cyclone separators

This paper constitutes an experimental study of the separation performances of a gas–liquid cylindrical cyclone (GLCC) separator that interests the oil industry. The global hydrodynamics behavior in the GLCC is characterized by flow visualization under various inflow operating conditions. The effect of the inlet nozzle design on the performances of the separator is studied by using three different nozzles, and it proves to be a key parameter. With an insufficient nozzle restriction, low swirl intensity is imparted to the flow. Due to inadequate centrifugal effects, liquid is prematurely carried over by the gas as flooding occurs in the separator upper part. High amounts of gas are also carried under by the liquid stream. On the other hand, with a too severe nozzle convergence, the important drag applied by the gas leads to liquid “short circuiting” the cyclone toward the gas outlet. In addition to the nozzle design, the separator performances are influenced by phenomena such as liquid bridging or the occurrence of the slug flow regime at the cyclone inlet. This paper leads to a better understanding of the links between the hydrodynamics in the GLCC and its operational limits, which is necessary to enable reliable scaling up tools.     

Investigation of the influence of inner-shell photoionization and photoexcitation on the Heα spectrum in photoionized plasmas

The present paper investigates the influence of inner shell photoionization and photoexcitation on the He_α, i.e., the 1s² to 1s2p transition in He-like ions, and the associated satellite spectra in photoionized plasmas. A comparison of the importance of these processes is made relative to other atomic processes as a function of the electron temperature and irradiation conditions. For the formation of the He_α and the satellite spectra, the K-shell photoionization is found to have significant contribution under low radiation temperature and/or intensity, when lithium- and beryllium-like ions have high abundance, but highly ionized H-like ions are rare.     

The effect of temperature correction on the measured thickness of formaldehyde zones in diffusion flames for 355 nm excitation

The temperature dependent corrections of the formaldehyde laser induced fluorescence raw signal are discussed for the 355 nm excitation, which is widely available as the third harmonic of Nd-YAG lasers. The temperature dependence of the HCHO partition function is calculated explicitly and the effect of quenching corrections is discussed in view of the absence of experimental data on collision cross-sections. Particular reference is made to the case of HCHO layers in hydrocarbon diffusion flames. It is shown that the thickness of such layers is not affected drastically by the calculated corrections, which has implications for the estimate of the scalar dissipation rate in diffusion flames.     

The effect of boundary curvature on the stress response of linear and branched polyethylenes in a contraction�Cexpansion flow

The effect of flow-boundary curvature on the principal stress difference (PSD) profiles observed through a contraction?Cexpansion (CE) slit flow is evaluated for three different polyethylenes exhibiting increasing levels of branching. Studies were performed using both experimental optical techniques and computational simulations, in the latter case to evaluate the ability of constitutive models to predict these complex flows. The materials were characterised using linear and extensional rheology, which were fitted to the multi-mode ROLIE-POLY and POM-POM models depending upon material branching. Three CE-slit geometries were used; with sharp corners, and with rounding equal to one quarter and one half of the slit length. These created a mixed, but primarily simple shear flow, with different levels of extension and shear depending upon the level of curvature. The PSD developed from an initial Newtonian profile to increasing levels of asymmetry between the inlet and the outlet flow as the level of material branching increased. The rounding was found to lead to the delocalisation of PSD within the flow and removal of the stress singularity from the corner of the CE-slit. It also led to a decrease in the pressure drop across the geometry and an ??opening out?? of features such as downstream stress fangs to create downstream ??crab-claws??. Matching between experiments and simulations for the time evolution of flow from start up for each material in the various geometries illustrated good agreement for both models.     

Study of the inertial effect and the nonlinearities of?the?CRONE suspension based on the hydropneumatic technology

In this paper, we emphasize two main effects involved in the CRONE car suspension technology (CRONE: French acronym for Commande Robuste d??Ordre Non Entier). In a first time, we present the influence of the inductive or inertial effect of the pipes that links the different cells of the hydropneumatic car suspension. These components are mainly resistive and capacitive devices. Then, we analyze the nonlinear relations that link the hydraulic power variables (the flow and the pressure) of the hydraulic resistors and the hydropneumatic accumulators and we study the effect of the nonlinear terms on the car suspension response. Our study is based on the gamma RC arrangement developed in Altet et al. (In: Analysis and design of hybrid systems??proceedings of ADHS03, pp. 63?C68. Elsevier, Amsterdam, 2003) and Serrier et al. (In: Proceedings of IDETC/CIE 2005: ASME 2005 international design engineering technical conferences and computers and information in engineering conference, Long Beach, CA, USA, 24?C28 September 2005). In a second time, we focus only on the gamma RLC arrangement, introduced in Abi Zeid Daou et al. (Int. J. Electron. 96(12):1207?C1223, 2009). We show whether the parasite effect due to the pipes or the nonlinear RC components affect the system??s response. The simulation results show that neither the inertial effect caused by these parasite pipes of one meter length nor the use of the nonlinear resistors or the accumulators modifies the response of the gamma RC arrangement.     

Investigation on the effect of density ratio on the convergence behavior of partitioned method for fluid–structure interaction simulation

In order to investigate the effect of density ratio of fluid and solid on the convergence behavior of partitioned FSI algorithm, three strong-coupling partitioned algorithms (fixed-point method with a constant under-relaxation parameter, Aitken’s method and Quasi-Newton inverse least squares (QN-ILS) method) have been considered in the context of finite element method. We have employed the incompressible Navier–Stokes equations for a Newtonian fluid domain and the total Lagrangian formulation for a non-linear motion of solid domain. Linear-elastic (hyper-elastic) model has been employed for solid material with small (large) deformation. A pulsatile inlet-flow interacting with a 2D circular channel of linear-elastic material and a pressure wave propagation in a 3D flexible vessel have been simulated. Both linear-elastic and hyper-elastic (Mooney–Rivlin) models have been adopted for the 3D flexible vessel. From the present numerical experiments, we have found that QN-ILS outperforms the others leading to a robust convergence regardless of the density ratio for both linear-elastic and hyper-elastic models. On the other hand, the performances of the fixed-point method with a constant under-relaxation parameter and the Aitken’s method depend strongly on the density ratio, relaxation parameter selected for coupling iteration, and degree of deformation. Although the QN-ILS of this work is still slower than a monolithic method for serial computation, it has an advantage of easier parallelization due to the modularity of the partitioned FSI algorithm.